The excited-state isomerization of auramine in 4-butyl-1-methylimidazolium hexafluorophosphate (BMIM-PF6) has several anomalies compared to the same reaction in nonionic solvents.  In BMIM-PF6, the reaction kinetics (1) become highly dispersed, i.e., nonexponential, (2) lose their induction period, and (3) develop a long-lived (> 2 ns) component.   A new, multidimensional spectroscopy, multiple population-period transient spectroscopy (MUPPETS), is used to determine the origin of these effects.  MUPPETS decomposes the nonexponential kinetics into homogeneous and heterogeneous components.  The heterogeneity is broad-a factor of 70 from 10�90% points of the distribution-but homogeneous effects are also important.  The rate heterogeneity is assigned to variation in the local electric field rather than in the local viscosity.  The long-lived component is assigned to a second excited-state channel, not to a second ground-state conformer.  The induction period persists in the ionic liquid, but is obscured by heterogeneity in standard measurements.

Excited-state isomerization in an ionic liquid: MUPPETS (multiple population-period transient spectroscopy) studies of auramine in BMIM-PF<sub>6</sub>

243rd National Meeting (2012)

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Excited-state isomerization in an ionic liquid: MUPPETS (multiple population-period transient spectroscopy) studies of auramine in BMIM-PF6

Excited-state isomerization in an ionic liquid: MUPPETS (multiple population-period transient spectroscopy) studies of auramine in BMIM-PF₆